CZ303296B6 - Belite clinker and process for producing thereof - Google Patents

Abstract

In the belite clinker formed by belite, tricalciumaluminate, tetracalciumaluminoferrite, alite and free lime, the fraction of the alite component is at the most 20 percent by weight and in the clinker chemical composition the fraction of SOi3 is in the range of 2.0 to 7.0 percent by weight wherein the occurrence of other phase components of the clinker containing sulfur, yeelimite and anhydrite is restricted in the sum to a value of up to 5.0 percent by weight. The clinker is produced such that a raw material with the high content of SOi3 is added into a raw material flour intended for clinker firing, wherein the amount of SOi3 in the clinker is controlled in the range of 2.0 to 7.0 percent by weight whereupon the clinker is fired in a cement revolving furnace.

Description

Bleaching shade and method of its production

Technical field

BACKGROUND OF THE INVENTION The present invention relates to a composition of belite-based cement clinker formed in addition to belite, tricalciumaluminate, tetracalciumaluminate terite, alite and free lime, and to a process for its manufacture.

BACKGROUND OF THE INVENTION

Belitic clinker, a clinker consisting solely of belite and mass boundaries, i.e. a melt filling the space between belite crystals, composed of tricalciumaluminate and tetracalciumaluminateferite, is not produced because it has been found to have unsatisfactory strengths to date. Whitening in conventional port 15 clinker clinker has significantly lower hydraulic activity compared to alite and contributes only significantly to strength after 28 days of hydration. This is confirmed by a laboratory-prepared sample labeled SB, whose composition and properties are shown in Example 1. However, bleach provides a more resistant hydrated matrix than an alite-rich classic Portland cement in terms of structural resistance. In addition, if mass production of low-carbonated belitic clinker could be solved, this would mean considerable energy savings and reduced CO ₂ emissions.

The hitherto known methods of belite activation mostly followed directions which are beyond the scope of current furnace lines. Published works deal with polymorphic belite on one hand and properties of its stabilized modifications, on the other hand with properties of clinker with various contents of these modifications and their influence on cement strength. The results of these studies are not very encouraging, because reducing lime saturation below the currently used interval (90-100%) leads to a decrease in alite content and thus a sharp decrease in strength. Studies have led to the conclusion that bleaching in current alitic-belitic cements has little hydraulic activity.

Stabilization of more active forms of belite was achieved only by increasing the concentration of alkali oxides and extreme cooling rates. More recently, the so-called remelting reaction is used for the hydraulic activation of belite, where by controlling the temperature of the cooling and controlling the admixture content, phase transitions associated with the release of the liquid phase and the disintegration of the belite crystals occur. However, these methods are realized in a laboratory or on special equipment, ie under conditions beyond the possibilities of current production technologies.

To a limited extent, sulfoaluminate belitic cements (SAB) are produced which exhibit quite good properties. The main hydration product of these cements, ettringite, with its extreme crystalline water content, ensures a rapid increase in initial strength, but does not give a guarantee for the long-term stability of the concrete. Experiments were also conducted with the industrial production of sulfoferoaluminate belitic clinker (SFAB) and high-ferrous belitic clinker (HFBC), which had satisfactory strengths after 28 days of hydration but low short-term strengths. The furthest in this respect is China, where, besides SAB cements, fluoroaluminate belitic cements and highly belitian Portland cements with 20 to 30 wt. alitu.

The Applicant's research has shown that the hydraulic activity of belite depends not only on its modifications but also on the method of preparation and the conditions of belite formation. This confirms the original conclusion that individual modifications of belite can be hydraulically highly inactive or almost inactive depending on the type of formation.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a composition of belitic clinker which is sufficiently hydraulically active and at the same time can be produced using existing technological lines and the cement produced from it with its properties approximates port I and alite predominant cement.

SUMMARY OF THE INVENTION

Cement clinker consists of the following components:

- bleach = (dicalciumsilicate + isomorphic impurities)

- alite = (tricalciumsilicate + isomorphic impurities) to - tricalciumaluminate

- tetracalciumaluminátferit

- loose lime.

The essence of the clinker according to the invention consists in that the proportion of alitic component contained in it is max. 20% by weight, in the chemical composition of the clinker there is a proportion of SO ₃ in the range of 2.0 to 7.0% by weight. components containing sulfur - yeelimitu (Catauí ^ SOO) and anhydrite _(CaSO4) -is in the sum is limited to 5.0%.

Indeed, it has been shown experimentally that as the amount of SO ₃ in the clinker increases, its concentration increases in the belite crystal while increasing the CaO: SiO ₂ ratio in favor of CaO. This bleach ('sulfobelite') is then hydraulically more active than the normal bleach contained in conventional Portland clinker. In addition, if alite is present in the clinker, it is stabilized by the SO ₃ effect in the form of a modification Mi, which has a higher hydraulic activity than the more conventional modification M ₃ .

The cement clinker of this composition is produced by adding a high SO ₃ content of raw meal to the clinker firing, controlling the SO ₃ content of the clinker in the range of 2.0 to 7.0% by weight, and then the clinker burns in a cement rotary kiln.

Various types of waste gypsum or fluidized fly ash can be added to the raw meal.

DETAILED DESCRIPTION OF THE INVENTION

Example 1:

Four types of clinkers were burnt from common cement raw materials under laboratory conditions. Two SO ₃ doped clinker clinkers with different lime saturation - hereinafter referred to as S-B80S4 and SB90S4. For comparison, purely belitic clinker labeled SB and standard Portland clinker with high alite content labeled SA are standard. Their phase and chemical composition in wt. is in the following table:

Stinek S-B S-B80S4 S-B90S4 S-A Firing temperature (”C) 1400 1400 1400 1450 Burning time (min) 40 40 40 120 Phase composition alit 0.2 0 8.3 66.7 bleach 79.3 81.3 71.5 12.2 tricalciumaluminát 4.0 2.6 4.1 12.3 tetracalcíumaluminátferlt 16.5 14.6 13.6 7.8 free lime 0 0 0 0.9 yeelimit 0 tracks tracks 0 anhydrite 0 1.5 2.5 0 Chemical composition - choice SiO ₂ 27.03 24.08 23.04 22.63 ai ₂ o ₃ 5.49 5.47 4.79 4.80 Fe ₂ O ₃ 3.90 3.68 3.31 2.77 MgO 1.05 1.08 1,02 1.04 CaO 59.65 58.70 59.84 66.23 SO ₃ total 0.06 4.44 4.43 0.03 SLP 70.4 77.0 82.7 93.5 Ms 2.88 2.63 2.84 2.99 Ma 1.41 1.49 1.45 1.73

SLP, Ms and Ma are the basic chemical parameters: SLP = Lea-Parker lime saturation

Ms = silicate module

Ma = aluminate module

Cements made from these clinkers with the same solidification regulator content and approximately the same specific surface area have the standardized technological properties, which are listed in the following tables:

Specific weight in kg / m ³ and specific surface in m ² / kg of prepared cements

Cement C-B C-B80S4 C-B90S4 C-A Density 3230 3261 3191 3179 Specific surface 435 436 438 437

-3 CZ 303296 B6

Cement strengths in MPa determined according to ΕΝ 196-1

Cement 2 days 7 days 28 days 56 days 90 days Bend Pressure Bend Pressure Bend Pressure Bend Pressure Bend Pressure C-B 1.8 2.0 1.3 2.3 3.9 14.6 5.1 31.1 5.7 38.3 C-B80S4 0.4 1,8 2.3 12.2 6.9 47.4 8.7 57.8 6.3 60.6 Č-B90S4 2.8 11.0 3.4 24.2 7.4 51, Ϊ 9.4 61.5 8.7 65.8 C-A 3.7 16.6 7.3 44.7 8.4 66.3 7.9 70.8 8.3 69.5

Determination of solidification process, normal cementitious consistency and volume stability according to EN 196-3

Cement Normal consistency (%) Start of solidification (h: min) Setting time (h: min) Volume stability (mm) C-B 30.7 1:00 1:30 0.0 C-B80S4 30.3 4:20 5:40 0.8 C-B90S4 28.7 4:00 5:10 0.3 C-A 28.0 3:50 4:40 0.2

io Hydration heat of cements determined according to ΕΝ 196-8

Cement Hydration heat [kJ / kg] 2 days 7 days 28 days 56 days 90 days C-B 118 140 237 286 325 C-B80S4 120 154 286 312 327 C-B90S4 174 195 290 323 346 C-A 230 311 449 475 487

Example 2:

From common cement raw materials, belitic clinker labeled S-BS3 doped with SO ₃ was burned in a special model rotary kiln at a temperature of 1350 to 1400 ° C with the following phase and chemical composition in% by weight:

-4GB 303296 B6

Clinker S-BS3 Phase composition alit 1.9 bleach 80.2 tricalciumaluminát 4.7 tetracalciumaluminátferit 13.2 free lime υ yeelimit tracks anhydrite tracks Chemical composition - selection SrO ₂ 24.75 AI ₂ O ₃ 4.66 FejO, 3.95 MgO 1.39 CaO 60.40 SO ₃ total 3.39 SLP 78.1 Ms 2.88 Ma 1.18

SLP, Ms and Ma are basic chemical parameters:

SLP = Lea-Parker lime saturation

Ms - silicate module Ma = aluminate module

From said belitic clinker cement was prepared by grinding with 2.5 wt. gypsum as well as solidification regulator to specific surface 350 m ^from .kg “'(designation C-A0B100). As a comparative standard, cement with the same specific surface area was prepared from conventional industrial Portland clinker with a high alite content with the addition of 5 wt% gypsum (ref. C-A100B0).

Furthermore, the properties of mixed cements from these two basic cements were studied, because 15 different dosages can be used to prepare cements with controlled technological properties according to the user's requirements (final strength, course of strength increase, released hydration heat, etc.).

The strength results are given in the following table (the number in the cement designation for letter A indicates the percentage of alitic cement and for letter B the percentage of belitic cement):

-5GB 303296 B6

Compressive and flexural strength according to Ε 196-1 in MPa of prepared mixed alitic-belitic cements

Designation cement Hydration time 2 days 7 days 28 days Pressure Bend Pressure Bend Pressure Bend C-A100B0 29.8 5.2 50.4 7.9 63.6 8.6 C-A8GB20 22.9 4.0 45.5 7.8 67.6 8.4 C-A60B40 17.3 3.2 40.5 6.7 73.9 7.0 C-A40B60 13.5 2.2 29.6 5.5 76.4 7.8 C-A20B80 5.7 1.3 17.6 3.9 79.8 8.2 C-A0B100 1,2 0.5 7.1 2.4 69.3 7.5

Determination of normal density and setting and end of solidification according to ΕΝ 196-3

Sample Normal density <%) Start of solidification (h: min) End of setting (h: min) C-A100B0 27.3 4:10 5:00 C-AOB100 27.6 3:50 4:40

For pure C-AOBIOO cement, the heat of hydration was also determined after 7 days of hydration using the EN 196-8 dissolution method of 178 kJ / kg. It can therefore be classified as a cement with very low hydration heat.

is In the production of mixed cements composed of common alitic clinker and this special belitic clinker, up to 40% replacement of excellent initial strength can be achieved and in addition, by changing the ratio of both clinkers, special cements with properties can be prepared according to their application requirements.

Claims (3)

PATENT CLAIMS 25 1. Belitic clinker consisting of the following components: belite, tricalciumaluminate, tetracalciumaluminateferite, alite and free lime, characterized in that the proportion of the alithic component contained in it is max. 20% by weight, in the chemical composition of the clinker there is range 2.0 to 7.0% by weight, while the presence of other phase components containing yeelimite sulfur (Ca ₄ Al ₆ O ₁₂ (SO ₄ )) and anhydrite (CaSO ₄ ) - is limited to a value of up to 5.0% 30 wt. -6GB 303296 B6 The method for producing Belgian clinker according to claim 1, characterized in that a raw material with a high SCh content is added to the raw meal for clinker firing, wherein the SO ₃ content of the clinker is controlled in the range of 2.0 to 7.0% by weight. , then the clinker is burned in a rotary kiln, Method according to claim 2, characterized in that different types of waste gypsum or fluidized fly ash are added to the raw meal.